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UNSTEADY EULER algorithm WITH UNSTRUCTURED DYNAMIC MESH FOR COMPLEX-AIRCRAFT AERODYNAMIC ANALYSIS

AIAA JOURNAL 1991年第3期29卷 327-333页

作者： BATINA, JT NASA Langley Research Center Hampton Virginia 23665

An Euler solution algorithm is presented for unsteady aerodynamic analysis of complex-aircraft configurations. The flow solver involves a multistage Runge-Kutta time-stepping scheme that uses a finite-volume spatial discretization on an unstructured grid made up of tetrahedra. A significant contribution of the research is the development and implementation of a moving mesh algorithm that is employed for problems involving static or dynamic deformation of the aircraft. The mesh algorithm is a general procedure that can treat realistic motions and deformations of complex-aircraft configurations. Steady and unsteady results are presented for a supersonic fighter configuration to demonstrate applications of the Euler solver and dynamic mesh algorithm. The unsteady flow results were obtained for the aircraft oscillating harmonically in a complete-vehicle bending mode. Effects of angle of attack and reduced frequency on instantaneous pressures and force responses were investigated. The paper presents descriptions of the Euler solver and dynamic mesh algorithm along with results that assess the capability.

关键词： Boeing 747 Lift Coefficient Aircraft Configurations Unstructured Grid Flow Conditions Unsteady Aerodynamic Analysis solution algorithm Aerodynamic Simulation Euler Equations Canard

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Finite volume discretization aspects for viscous flows on mixed unstructured grids

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AIAA JOURNAL 1999年第2期37卷 177-184页

作者： Haselbacher, A McGuirk, JJ Page, GJ Univ Loughborough Dept Aeronaut Engn Loughborough LE11 3TU Leics England

A solution method for compressible turbulent flows on unstructured grids in two dimensions is described. The method can be used on grids consisting of triangular and/or quadrilateral cells. Control volumes are constructed from dual cells, and the solution variables are stored at the vertices of the grid. Grid-transparent algorithms are developed that do not require knowledge of cell types, leading to simple discretization schemes on mixed grids. The inviscid fluxes are computed from limited high-resolution schemes originally developed for unstructured triangular grids. They are easily applied to quadrilateral or mixed grids and are grid transparent. The discretization of the viscous fluxes is studied in detail. A positive, grid-transparent discretization of Laplace's equation is developed, The existence of tangential derivatives in the viscous terms prevents grid transparency. By neglecting tangential derivatives, an approximate form of the viscous fluxes is developed, which recovers grid transparency. The approximate form is shown to be similar to the thin-shear-layer approximation. Results are obtained for a transonic inviscid flow, a laminar separated flow, and a transonic turbulent flow. Different control-volume constructions and quadrilateral, triangular, and mixed grids are assessed using a grid-refinement study. The approximate form of the viscous fluxes is investigated in detail.

关键词： Unstructured Grid Laplace Equation Shear Layers Viscous Flow NACA 0012 solution algorithm Eddy Viscosity Navier Stokes Equations Euler Equations Eddy Viscosity Turbulence Models

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PROBABILITY DENSITY-FUNCTION APPROACH FOR MULTIDIMENSIONAL TURBULENT-FLOW CALCULATIONS WITH APPLICATION TO IN-CYLINDER FLOWS IN RECIPROCATING-ENGINES

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AIAA JOURNAL 1991年第2期29卷 208-218页

作者： HAWORTH, DC ELTAHRY, SH General Motors Research Laboratories Warren Michigan 48090

The probability density function (pdf) method is extended to two- and three-dimensional transient turbulent flows. The numerical approach couples a Lagrangian Monte Carlo method to solve for the joint pdf of velocity and scalar compositions with an Eulerian finite-volume algorithm to calculate mean pressure and a turbulence time scale. A general approach applicable to variable-density chemically reacting flows has been taken;the present results are for nearly uniform density inert flows. Three engine-like configurations have been investigated: 1) a noncompressing axisymmetric cylinder-piston assembly with a central port;2) a noncompressing axisymmetric cylinder-piston assembly with an annular port;and 3) a compressing three-dimensional configuration with an off-center valve. Pdf results are compared with measurements and with conventional k-epsilon calculations for the two axisymmetric geometries. For these noncompressing flows the pdf approach is found to have little advantage over a k-epsilon model. Mean velocity profiles from both models are in good agreement with experiment for the central port case, whereas agreement for the annular port is less satisfying. Root-mean-square axial velocities from both models are low at early times in the intake process, but improve later in the cycle. Influence of numerical parameters on solution accuracy is assessed. The present work confirms the feasibility of the pdf approach for complex turbulent flows and represents an intermediate step in the application of pdf methods to multidimensional turbulent reacting flows, where they are expected to offer their greatest advantage.

关键词： Reciprocating Engine Kinematic Viscosity Axisymmetric Flow Monte Carlo Method Chemically Reacting Flow Reynolds Stress Kinetic Energy Turbulence Models Number of Particles solution algorithm

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Mathematical modeling of pressure on the strengthening vertical shaft support in "Mir" mine located in the Charsk saliferous rock series

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JOURNAL OF MINING SCIENCE 2006年第2期42卷 113-121页

作者： Konstantinova, S. A. Chernopazov, S. A. Ural Sci Res & Design Inst Halurgy Perm Russia

The problem statement and the solution algorithm are presented for the case of contact between strengthening vertical shaft support and rocks. Hereditary viscoelasticity equations are used as constitutive relations for saliferous rocks. An analysis of the dynamics of the growing pressure on the support is performed versus the shaft cross-section occurrence depth, saliferous rock strength on the contact, and spacing between the rock contour and the support in the shaft.

关键词： model of contact stress-strain state hereditary viscoelasticity solution algorithm pressure on support

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Solving discrete linear bilevel optimization problems using the optimal value reformulation

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JOURNAL OF GLOBAL OPTIMIZATION 2017年第2期68卷 255-277页

作者： Dempe, S. Kue, F. Mefo TU Bergakad Freiberg Dept Math & Comp Sci Freiberg Germany

In this article, we consider two classes of discrete bilevel optimization problems which have the peculiarity that the lower level variables do not affect the upper level constraints. In the first case, the objective functions are linear and the variables are discrete at both levels, and in the second case only the lower level variables are discrete and the objective function of the lower level is linear while the one of the upper level can be nonlinear. algorithms for computing global optimal solutions using Branch and Cut and approximation of the optimal value function of the lower level are suggested. Their convergence is shown and we illustrate each algorithm via an example.

关键词： Bilevel programming solution algorithm Discrete parametric optimization Global optimization

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Local time-stepping algorithm for solving probability density function turbulence model equations

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AIAA JOURNAL 2002年第9期40卷 1755-1763页

作者： Muradoglu, M Pope, SB Cornell Univ Sch Mech & Aerosp Engn Ithaca NY 14853 USA Cornell Univ Sibley Sch Mech & Aerosp Engn Ithaca NY 14853 USA

A local time-stepping algorithm has been developed to improve the numerical efficiency of Lagrangian particle-based Monte Carlo methods for obtaining the steady-state solutions of the modeled probability density function equations of turbulent reacting flows. On each step in the pseudo-time-marching algorithm, the properties of each particle are advanced by a time step, the magnitude of which depends on the particle's spatial location. This algorithm has been incorporated into the consistent hybrid finite volume/particle method. The performance of the local time-stepping method is evaluated in terms of numerical efficiency and accuracy through application to a non-reacting bluff-body flow. For this test case, it is found that local time stepping can accelerate the global convergence of the hybrid method by as much as an order of magnitude, depending on the grid stretching. Additionally, local time stepping is found to improve significantly the robustness of the hybrid method mainly due to the accelerated convection of error waves out of the computational domain. The method is very simple to implement, and the small increase in CPU time per step (typically 3%) is a negligible penalty compared to the substantial reduction in the number of time steps required to reach convergence.

关键词： Probability Density Functions Turbulence Models Kinetic Energy Monte Carlo Method Conservation Equations solution algorithm Number of Particles Convection Sandia National Laboratories Turbulence Kinetic Energy

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EFFECT OF CONTACT SPACING ON EFFICIENCY OF FLAT-PLATE SOLAR COLLECTORS

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JOURNAL OF SPACECRAFT AND ROCKETS 1985年第6期22卷 585-591页

作者： CRHA, S SCHNEIDER, GE Dep. Mech. Eng. Univ. Waterloo Waterloo Ont. Canada

The attachment of an extended surface to an energy removal tube in a noncontinuous manner is considered. Rather than to provide continuous weld or solder to form thermal contact, the use of uniform distribution of finite regions of contacts is examined. In particular, the application to solar energy collection is considered whereas discrete, discontinuous system of contacts offers potential economic benefit in the fabrication and reliability aspects of construction. The problem is formulated mathematically in nondimensional terms and numerical solutions employing the finite element method are obtained. It is found that the discontinuous nature of the weld can significantly degrade system performance with the degree of degradation strongly dependent on the fin surface Biot modulus.

关键词： Flat Plate Solar Collector Finite Element Method Thermal Performance Solar Energy Heat Transfer Coefficients Natural Convection Energy Transfer Heat Exchangers Thermal Conductivity solution algorithm

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Mean value analysis of military airlift operations at an individual airfield

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JOURNAL OF AIRCRAFT 1999年第5期36卷 750-755页

作者： Dietz, DC USAF Inst Technol Dept Operat Sci Wright Patterson AFB OH 45433 USA

An analytical queueing network model of airlift operations at an individual airfield is developed and implemented. The airfield system is represented as a capacitated open network of multiserver queues and fork-join constructs that capture concurrent aircraft flow through subnetworks of activities. Generated performance measures include mean values for system throughput, aircraft ground time, and resource utilizations, The quality of the analytical approximation is demonstrated through comparison with simulation results.

关键词： Airlift Airfields Aircraft on Ground Cumulative Distribution Function Air Mobility Command and Control Systems Software Development solution algorithm Aircraft Landing Air Forces

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ANALYSIS OF COMPLEX HYPERSONIC FLOWS WITH STRONG VISCOUS INVISCID INTERACTION

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AIAA JOURNAL 1988年第7期26卷 832-840页

作者： POWER, GD BARBER, TJ United Technologies Research Center East Hartford Connecticut

Two methods to improve the efficiency of predicting viscous/inviscid interaction in hypersonic flow are examined using an explicit full Navier-Stokes and a parabolized Navier-Stokes procedure. For the first method, a coarse grid full Navier-Stokes result is obtained that resolves the interaction effect of the viscous layer on the inviscid flowfield. In order to enhance the calculation of the surface normal gradients, the results of the coarse grid calculation are then used as initial and boundary conditions for another full Navier-Stokes calculation on a refined grid. Comparisons with benchmark experimental data indicate that this approach yields accurate skin friction and wall heat transfer at a substantially reduced computational cost compared to an initial fine grid calculation. The second method is based on a modification of a parabolized Navier-Stokes procedure to properly include upstream influence effects in the strong interaction region. In this approach, the stream wise pressure gradient term has been modified to account for the propagation of pressure waves within the subsonic layer through a global pressure iteration approach. Using this improved algorithm, good agreement with wall pressure, skin friction, and heat transfer is obtained compared with both experimental data and full Navier- Stokes results. The global pressure iteration scheme demonstrates a considerable reduction in computational time and memory requirements compared to the full Navier-Stokes procedure. © 1988 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： Hypersonic Flows Skin Friction Accurate Heat Transfer Prediction Navier Stokes Calculations Boundary Layer Equations Adverse Pressure Gradient CFD Mach Numbers solution algorithm Shock Layers

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Mathematical modeling of the stress-strain state in rock and artificial masses during slice chamber mining of underpit reserves in the "Internatsionalnaya" kimberlite pipe

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JOURNAL OF MINING SCIENCE 2005年第3期41卷 215-224页

作者： Konstantinova, SA Chernopazov, SA Ural Sci Res Perm Russia Planning Inst Halurgy Perm Russia

The statement and solution algorithm are proposed for the problem on the stress-strain state of a kimberlite body, filling massif, and enclosing rock during slice chamber mining with filling. The equations of nonlinea... 详细信息

关键词： stress-strain state filling model hereditary viscoelasticity solution algorithm

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